Unlike physical keys, touch screen targets do not have tactile indicators for accurate finger presses. Therefore touch screen targets have a large variability for accuracy among users and includes handedness biases. For good touch targets, existing literature has recommended target sizes 7- to 10-mm in approximate diameter. Given current real-estate constraints in touch screen displays, it is difficult to fit a full QWERTY layout without adding plurality in the keys (multiple key assignments to the same touch area).
There are three existing general solutions that fail to provide an optimum user experience. In one existing solution, the key sizes are maintained at recommended valued and plurality in keys are introduced (i.e., multiple characters assigned to the same key). In a second solution, key singularity is maintained and the key size is reduced. In a third solution, post-hoc correction is provided. With each of these techniques there are further enhancements that attempt to provide a better user experience. For example, with a maintained key singularity and reduced key size, one alternative can provide visual confirmation (in a main screen region) of a user intended key press and further provide disambiguation of simultaneous key presses (which are likely to occur with the smaller key sizes). In general, the existing enhancements still fail to provide a satisfactory user experience.